Molar heat capacities of alkanolamines from 299.1 to 397.8 K Group additivity and molecular connectivity analyses

Abstract

The molar heat capacities of 14 alkanolamine compounds have been measured at five separate temperatures in the range 299.1 to 397.8 K. These compounds were monoethanolamine (MEA), monomethylethanolamine (MMEA), dimethylethanolamine (DMEA), monoethylethanolamine (MEEA), diethylethanolamine (DEEA), n-propylethanolamine (n-PEA), diisopropylethanolamine (di-PEA), diethanolamine (DEA), methyldiethanolamine (MDEA), ethyldiethanolamine (EDEA), n-butyldiethanolamine(n-BDEA), tert-butyldiethanolamine (tert-BDEA), triethanolamine (TEA) and 2-amino-2-methylpropan-1-ol (AMP). Molar heat capacities of these compounds show a structural dependence, where the molar heat capacity of one molecule may be considered as the sum of various group contributions. Hence, the reported molar heat capacity data have been used as input to a group additivity analysis that yields estimates of CH ₂ , OH, NH and N group contributions to molar heat capacities at each investigated temperature. The additivity principle has been explored in more detail by using molecular connectivity indexes to obtain a simple five-term equation that models the molar heat capacities of the investigated alkanolamines over the entire experimental temperature range.